Data di Pubblicazione:
2008
Citazione:
Heparin Stimulates a Plasma Membrane Ca2+-ATPase of Arabidopsis thaliana / S. Meneghelli, L. Luoni, M. I. De Michelis. - In: JOURNAL OF BIOCHEMISTRY. - ISSN 0021-924X. - 143:2(2008), pp. 253-259.
Abstract:
We have studied the effect of heparin, a glycosaminoglycan widely used in releasing
tags from fusion proteins, on isoform 8 of Arabidopsis thaliana PM Ca2+-ATPase
(ACA8) expressed in Saccharomyces cerevisiae strain K616. Heparin stimulates
hydrolytic activity of ACA8 with an estimated K0.5 value for the complex of
15 1 mgml 1, which is unaffected by free [Ca2+]. Heparin increases Vmax up to
3-fold while it does not significantly affect the apparent Km for free Ca2+ and for the
nucleoside triphosphate substrate. The heparin effect is not additive with that of
exogenous calmodulin and heparin is ineffective on a mutant devoid of the
N-terminal auto-inhibitory domain ("74–ACA8). Altogether, these results indicate
that heparin activation is due to partial suppression of the auto-inhibitory function
of ACA8 N-terminus. Pull-down assays using heparin–agarose gel show that heparin
directly interacts with ACA8. Binding to the heparin–agarose gel occurs also with
a peptide reproducing ACA8 sequence 1M-I116. Several single-point mutations within
ACA8 sequence A56–T63 significantly alter the enzyme response to heparin,
suggesting that heparin interaction with this site may be involved in ACA8
activation. These results highlight a new difference between the plant PM Ca2+-
ATPase and its animal counterpart, which is inhibited by heparin.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Arabidopsis thaliana; Ca2+-ATPase; Calmodulin; Heparin; Plasma membrane
Elenco autori:
S. Meneghelli, L. Luoni, M. I. De Michelis
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